I was reading a post written by a guy who had just seen Norm Abrams' series on building kitchen cabinets. He was somewhat taken off guard by Norm's methods which included pocket-screwed face frames and screwed together plywood carcasses.
I know a guy who builds cabinets without using any plywood, screws, nails, staples or any other hardware except for Blum hinges and drawer glides. All of his interiors are made from solid lumber, glued to width. Everything is joined either with dovetails or mortise and tenon. He also does all of his own carving so his doors and drawer faces are often quite ornate and his installations are typically embellished with corbels, pilasters, carved elements, serpentine arches, etc. He works mostly in a hybrid French Country style or what we have come to call "California French." His jobs are always done on a time and materials basis and are typically ungodly expensive.
That is as high end work as I have ever seen a cabinet shop produce. So, if you want to go to the limit, that's where I would want to go. But most of us have been screwing plywood carcasses together for 95 percent of our cabinet work. We have also been screwing face frames together long before there were Kreg jigs and pocket hole boring machines. So, in this sense, Norm's cabinets are quite "typical" of the "average" set of kitchen cabinets. "Better" cabinets usually translates into better quality materials and hardware, more costly door designs and other embellishments. But the basic construction method remains the same.
Along with cabinets (lots of cabinets) I have, over the years, made a lot of furniture pieces and many smaller items like my chessboards and tables. Even a few chairs. And none of these have included any plywood or screwed joints or any of the things I might not think twice about doing when I build cabinets.
From time to time, I have encountered a degree of surprise when people realize that when I talk about high end work, I might actually be talking about screwed together plywood boxes. Many people understand that even within the limits of this standard construction method, there can be an enormous amount of variation in quality. But just as many are as surprised as the OP was that, on one level, their "high end custom" cabinets are going to be, in a very basic sense, made in the same manner as the cheap "box store" cabinets they just rejected.